1. Field of the Invention
The present invention relates to an office chair, and more particularly to a height-adjustable armrest structure.
2. Description of the Related Art
Referring to FIG. 1 that is a perspective view of a conventional office chair 10, a supporting portion 11 and an armrest portion 12 are disposed at both sides thereof, thereby forming an armrest assembly 13. In this way, both hands of the user can be placed on the armrest portions 12 for obtaining a comfortable sitting feeling. The conventional supporting portions 11 and the armrest portions 12 are integrally made of plastic by an injection molding process. Alternatively, the supporting portions 11 are made of metal whereupon the armrest portions 12 made of plastic are mounted on the supporting portions 11, thereby creating a fixed type structure that permits neither the height adjustment nor the angular adjustment. Thus, the individual requirements of the user are not fulfilled.
U.S. Pat. No. 6,062,646 disclosed an adjustable-height armrest in which the locking bolts are disposed at the center of the armrest carrier. This arrangement makes the height adjustment more difficult. In other words, an ergonomic operation interface is required for a convenient use. Furthermore, U.S. Pat. No. 6,948,775 discloses an office chair armrest that permits the angular adjustment as well as the forward and backward movement of the armrests. However, this structure does not achieve a height adjustment. It is important to provide the function of the height adjustment. The angular adjustment as well as the forward and backward movement of the armrests may have their substantial effects only when the function of the height adjustment is available. In other words, the angular adjustment as well as the forward and backward movement of the armrests won't provide the user with the optimal sitting feeling when the armrests are too high or too low.